Blockchain as a distributed ledger technology is suggested to address the weakness of a traditional data management system in VNs. In the FL-based EIS, blockchain can be used to provide a decentralized incentive mechanism, verify the trustworthiness of the updated model training, and support a fair global model's aggregation. Lately, some research has offered to merge FL and blockchain to strengthen privacy. In [1]}, the authors suggested a privacy-preserving data sharing mechanism in industrial IoT for a distributed multi-parties scenario. They integrate the consensus mechanism of permissioned blockchain with FL. Meanwhile, the work from [2]} designed the framework to refuse dishonest users from the FL system by automatically enforcing smart contracts to defy model or data poisoning attacks. Furthermore, the authors in [3]} proposed the DeepChain protocol that employs a blockchain-based incentive mechanism to provide a secure, auditable, fair, and distributed deep learning system. Here, the incentive is utilized to force participants to act rightly and substitute a centralized approach's drawbacks.
